Telephone system



W. C. PHEBUS TELEPHONE SYSTEM Filed Dec( 5, 1929 3 sheets-sheet 1 I L,william [1p1-Lehne Jgly 26, 193s.

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3 Sheets-Sheet 5 Filed Dec. 5, 1929 .SSQ @QQ I'LTE-TTD-T" william E.Fhehus Patented July 26, 193s PATENT OFFICE TELEPHONE SYSTEM lWilliam C.Phebus, Berwyn,

mesne assignments,

Ill., assignor, by

to Associated Electric Laboratories, Inc., Chicago, Ill., a corporationof Delaware Application December 5, 1929, Serial No. 411,714

28 Claims.

This invention relates to telephone systems in general, but is moreparticularly concerned with telephone systems for use in connection withrailroads. The object of the invention broadly stated is the provisionof new and improved apparatus and circuits for supplying telephoneservice on and between railroad trains and between trains and waysidepoints.

The utility of direct communication between railroad trains using thesame track systems and between trains and a wayside point, such as adispatchers ofce, has long been recognized, and numerous systems, bothtelephonie and telegraphic have been devised for this purpose. In f sofar as applicant is aware, none of these systems has been entirelysuccessful from a commercial standpoint due either to inherent operatingdefects or to excessive cost. Such systems may be divided roughly intotwo classes, namely; inductive telephone systems and radio telephonesystems. The instant invention may be identified as belonging to theinductive type and, therefore, only such systems will be discussed.

Basically the inductive train telephone system consists of a telephoneline inductively connected with telephone apparatus carried by a train.The method by which this connection is made varies considerably indifferent systems. It has been found most satisfactory, however, toemploy an intermediate circuit to which both the train apparatus and thetelephone line may be inductively connected as required. It is obviousthat if the rails of the track can be used as a part of the intermediatecircuit there will be considerable saving in conductors required forthis purpose. There are numerous obstacles in the way of such use, forexample the grounded condition of the rails and their electricaldiscontinuity for signalling purposes. Another obstacle 40- is the greatamount of inductive disturbance picked up by such circuits from nearbypower lines, electric railways, etc. These obstacles have beensuccessfully overcome in the instant invention, as will be pointed outhereinafter.

45 In order that the utility of the invention may be better appreciatedthe conditions under which it is to be used will be discussed brieiiy.In present day railroad practice the track is usually divided intoelectrically insulated sections 50 or blocks for signalling purposes.Each block is provided with relay equipment which is controlled bytrains passing through the block for the purposes of operating varioussignal mechanisms. In addition, some railroads are provided with systemsfor automatic train control,

the Intermittent Electrical Contact method, such as described inBulletin No. of the American Railway Association Committee on AutomaticTrain Control, published June, 1929, being more or less standard forthis purpose. Telephone apparatus must be capable of. functioning inconjunction with these signalling and control systems, withoutinterfering in any way with their operation.

It is an object of the invention to produce a telephone system whichwill operate satisfactorily under the above conditions without interfering in any way with existing signal and control apparatus, andwithout necessitating any major changes in such apparatus. Anotherobject is the utilization of existing apparatus to the fullest degree inorder that both first cost and upkeep may be reduced to a minimum. Otherobjects and features not specifically mentioned at this time will bediscussed along with the operation of the system, which will bedescribed in detail in later paragraphs, reference being had to theaccompanying drawings, comprising Figs. l to 8, inclusive of which Fig.l shows a side View of a railroad car with the inductor in place; Figs.2 and 3, are, respectively, an end view and a top view of the apparatusshown in Fig. l; Fig. 4 shows a section of track arranged to use therails as a part of the telephone circuit; Fig. 5 shows a transmittingand receiving set; Fig. 6 shows aV stretch of track arranged forsignalling from the train to the dispatcher; Fig. 'l shows anothersection of track arranged with a wire between the rails for talkingpurposes; and Fig. 8 shows a further modification of the track circuitdisclosed in Fig. 4.

Fig. l shows diagrammatically a side view of a railroad car equippedwith telephone apparatus. The inductor I which consists of a number ofturns of wire is mounted on a frame beneath the body I of the car at apoint between the rails over which the car runs. This coil or inductoris mounted sufficiently high to clear ordinary obstructions which may bepresent along the track, of which one rail 2, and ties such as l areshown. The inductor is connected to the telephone set TT by means of thetransformer 8. While no particular type of car is shown, it is to beunderstood that this apparatus may be mounted on a locomotive tender orthe locomotive itself, on the Caboose, or on passenger coaches withequal facility. Fig. 2, is an end view of equipment shown in Fig. 1 andillustrates the manner in which the inductor is mounted between thewheels. The inductor frame is normally carried in a vertical position asshown in Fig. 2, but may be turned to a horizontal position whenrequired for purposes which will be discussed hereinafter. In thisfigure is also shown a conductor 9 carried on the ties between therails. The purpose of this conductor will be fully explained in laterparagraphs.

Fig. 3 is a top View of equipment shown in Figs. 1 and 2, andillustrates the location of the inductor from another angle.

Fig. 4 shows a stretch of track divided into sections or blocks A to F,inclusive. The signalling apparatus for each block includes a relaybridged across the two rails at one end of the block, and a source ofcurrent or battery bridged across the rails at the other end of theblock. The signal relay is normally energized, and retracts itsarmatures only when it is short-circuited by the entry of a train intothe block. Alternate blocks, such as C and E` are provided with a relayconnected in series with the battery across the two rails. This relay isof relatively low resistance and is stily adjusted so that it does notoperate in series with the above mentioned signal relay. However, when atrain passes through the block a relatively low resistance circuitexists between the rails through the wheels and trucks of the train, andthe relay operates from the increased current flow.

The previously referred to intermediate circuit for connecting the traintelephone set with the dispatchers line is a closed loop circuit ofwhich the two rails of the block in parallel are connected by aconductor which is carried on a pole line adjacent to the track. It willbe noted that transformers are included in this circuit at each end ofthe block providing an inductive connection with the circuit of theadjacent block. However, alternate transformers, such as llTB and 4TD,are normally rendered ineiective by a short-circuit in one winding andthe opening of the other winding. It, therefore, follows that thecircuits of the two blocks are always inductively connected, and as willbe explained later, under certain conditions four, six, or more blocksmay be so connected.A The transformers are connected up so that atransposition exists between adjacent block circuits whether permanentlyor temporarily connected. Each pair of normally connected blockcircuits. is also provided with a transformer for inductively connectingthe circuit with the dispatchers line shown at the bottom of the sheet.This connection, however, in the present instance, is under the controlof the dispatcher and is brought about by the operation of a railwayselector S, which may be of any well known type. A pair of trucksrepresenting respectively the front and rear ends of a train are shownin blocks C and D. Each truck represents a car with an inductor, such asshown in Fig. l. The various relays are shown in normal condition withthe exception of those associated with blocks C and D, which are shownin the position which they assume on the presence of a train in therespective blocks.

In Fig. 5 is shown a telephone set with trans-4 mitting and receivingampliers for use in the telephone systems herein described. The circuitshown is connected with the dispatchers line referred to in Fig. 4, andalso with other dispatchers lines as will be pointed out later. It maybe noted that the telephone set designated TT in Fig. 1 is identicalwith the set shown in Fig. 5.

Each telephone set is provided with a push button which switches overthe set from talking to listening position, that is, either thereceiving amplifier or the transmitting amplier can be cut into serviceas required. The receiving amplier is normally connected up to thedispatchers line and to a loud speaker or other signal. A switch isprovided for switching over from the loud speaker to the telephone set.The dispatchers selector control equipment SC is shown in skeleton formas associated with the dispatchers line of Fig. 4. This apparatus iswell known in the art and, since it forms no part of this invention, adetailed description is not considered necessary.

In Fig. 6 is shown a modication of the system shown in Fig. 4. Themodification consists in providing means for signalling the dispatcherfrom the train. The apparatus for this purpose would normally beassociated only with certain blocks of the track system, as it is notconsidered necessary to permit the train to call the dispatcher at alltimes. This calling system makes use of the ramp type automatic traincontrol apparatus previously referred to and is, of course, providedonly in systems using such type of automatic train control. Theoperation of the system disclosed in this figure, aside from the abovementioned connecting arrangement is identical with that shown in Fig. 4.It may be further noted that the dispatchers line shown at the bottom ofthe sheet and immediately below Fig. 6 extends to a telephone set, suchas the set shown in Fig. 5. It may also be noted that the train or carrepresented as standing in block C corresponds to the equipment shown inFig. 1.

In Fig. 7 is shown a still further modification of the system disclosedin Fig. 4. In this case the wire forming a part of the intermediatecircuit is located between the rails and is carried by the ties, asshown in Fig. 2. As illustrated, only one rail is used in the presentinstance, although it is obvious that two rails in parallel can be usedequally well by placing the conductor in the center of the track.Further, the connection between the block circuits is direct instead ofinductive as shown in the previous cases. The block connections are soarranged that a transposition exists between adjacent blocks. Thedispatchers line and selectors which control the connections thereto arethesame as those shown in Fig. 4, and the line likewise terminates in atelephone such as shown in Fig. 5. When used in connection with thisparticular arrangement, the inductor shown in Figs. 1 and 2 is carriedin a horizontal position, instead of the vertical position shown.

Fig. 8 is a further modification of the apparatus shown in Fig. 4. Thisarrangement contemplates the use of a three winding induction coilinstead of the two winding coils used in previous cases. A furthermodication of the relay apparatus is shown, it being assumed that theblocks are equipped with bridge relays of the normally energized typeinstead of the bridge and series relay shown in Fig. 4.

Before proceeding with the description of the operation of the varioussystems, the operation of the telephone set Fig. 5 will be considered.This set, which is used both for the train apparatus and for thedispatchers line shown in the various gures, consists essentially of areceiving amplifier and a transmitting amplifier as previously stated.'I'hree stages of amplification are provided by the amplifying tubesRAI, RAZ, and RAS. The Various stages are transformer coupled, thesetransformers being of the usual iron core type particularly designed forhandling currents of audio frequency. The primary winding of the inputtransformer 5TI is bridged across the dispatchers line, as shown, orwhen the set is used connection with theY train apparatus, is connectedto the train inductor by means of a connecting transformer such as shownin Fig. 1. The secondary winding of the input transformer is connectedupr so that the voice current from the dispatcliers line will varythegrid potential of the first amplifier tube RAI. The usual interstagetransformers 5T2, and 5T3 connect up the second and third stages ofamplification. An output transformer 5T4 serves `to connect the lastamplifying tube with the receiving apparatus. It will be noted that adouble pole switch DS is provided for connecting this transformer toeither a loud speaker LS or to the telephone set comprising the receiverREC and transmitter TR. 'I'he switch will normally be thrown to itsupper position which places the loud speaker in service and consequentlyany signals coming in over the dispatchers line or train inductor, willbe amplified and put through the loud speaker which will 'serve as asignal for incoming calls. The transmitter amplifier consists of twotransformer coupled amplifying stages using the well known three elementvacuum tube. The input transformer ST5 has its primary winding connectedin series with the transmitter TR of the telephone set. A resistance Rin this circuit reduces the drain on the battery. 'I'he resistance isbridged by a condenser which provides a low resistance path for thevoice current. The secondary winding of the output transfomer 5T? isadapted to be connected to bridge the dispatchers line, or to the traininductor when the setis used with such apparatus, by switching relay SR.This relay is controlled by a key K associated with the telephone setand is operated only when it is desired to speak over the set. Relay SR,when operated, completes the battery feed circuit for the filaments ofthe amplifying tubes TAI and TAZ at its lower armature, connects thesecondary winding of the output transformer 5T'I across the dispatchersline at its upper-inner armature, and at this armature also disconnectsthe primary winding of the input transformer STI of the receivingamplifier froml the line, and at the uppermost armature opens thebattery feed circuit for the laments of the amplifying tubes RAI, RA2,and RAS of the receiving amplifier.

It is obvious from the foregoing that when receiving a message the key Kis left in normal position and when transmitting a message this key isoperated. The Voice currents produced by the transmitter 'IR areamplified by the transmitting amplifier and impressed on the line orinductor in the well known manner, and such voice currents on the lineare transferred to the inductor by way of the intermediate circuit orvice versa and are amplified by a receiving amplier similar to the oneshown and impressed on the receiving loud speaker or receiver of thatset.

With the operation of the telephone set in mind the manner in whichvarious calls may be made in the system disclosed will now beconsidered.

Referring now to Fig. 4, front and rear ends of a train are shown',respectively, in blocks C and D as previously stated. The first and lastcar of the train are provided within'ductors I and telephone sets, suchas Fig. 5, connected up as shown in Fig. 1. Assume that the trainman atthe rear car TRR desires to speak with the engineer or trainman at firstcar orv locomotive TRF ofthe train. The train may be either stationaryor in motion, the operation being the same in either case as long as thetwo inductor carrying cars are in the blocks mentioned. The calling manoperates th-e transmitting key of his telephone set, as was describedunder Fig. 5, and speaks into the transmitter thereby impressing anamplified current on the inductor I. This current is induced in theintermediate circuit by way of the two track rails in parallel, thecircuit extending from the right end of the rails of section D, throughthe two condensers connected thereto, normally closed middle contacts ofthe relay 42E, through the right-hand winding of the transformer ATL',through the normally closed lower contacts of the relay 42E, thence overthe intermediate conductor 43, through the right-hand winding of thetransformer 4TC, through two condensers in parallel to the left-hand endof the rails of block D. 'Ihe current in the block circuit is in turninduced in the block circuit adjacent to the left, this circuitextending from the left-hand winding of the transform-er 4TC, throughthe normally closed upper contacts of the relay 4TB, through the twocondensers in parallel, to the left-hand end of the rails of the blockC, through those rails in parallel and through the two condensers at theright end of the rails back to the left-hand winding of the transformer.The current flowing in this circuit will in turn be induced into theinductor I of the front car TRF, and, after being amplied by a receivingamplifier, such as Fig. 5, operates the loud speaker LS. The calling manmay transmit orders to the called man by way of the loud speaker asdescribed, or, if it is desired to hold a conversation, may so informthis party. The called man will then disconnect the loud speaker andconnect up the telephone set by means of a switch, such as switch DS,and by operating the corresponding talking key K of his set may speak tothe calling man over the circuits just traced. The calling man in orderto hear the conversation must, of course, release his talking key K, aspreviously explained.

It will be noted that the transformer IITL is ineluded in this circuitbut this is without effect at this time since the primary winding of thetransformer is open at the contacts of the selector S. Further theleft-hand winding of the transformer ATD is short-circuited at thenormally closed lower contacts of relay 42E, thereby, keeping the blocksD and E isolated. Blocks B and C are isolated by the open point in theright-hand winding of the transformer II'IB.

A block circuit may vary in length from a few.

yThis reversal has the effect of a transposition,

and the inductive disturbance picked up by each block beingapproximately the s-ame, the effect will be to neutralize thedisturbance and reduce the noise considerably. The voice current is notaffected by this transposition and consequently reliable transmission isattained.

Inthe foregoing description it was assumed that CII the inductors shownwere located at*v different points on the same train. It is obvious,however, that the same results would be obtain-ed if these inductorswere carried by separate trains. Further the dispatcher may talk witheither party in the above connection by merely operating the selector S'to connect up the left-hand winding of the transformer GTL' to thedispatchers line. In this manner, orders from thedispatcher as well asinformation from the trainmen may be passed back and forth.

The above described intermediate circuit would be effective with thetrain in either of the blocks C or D alone. With the train in block Cthe signal relay l ID would be actuated and the previously tracedcircuit including the conductor 43 would extend through lower and middleclosed contacts of this relay. The blocks D and E would be isolated bythe short-circuit around the left-hand winding of the transformer JTD asbefore. With the train in section D alone the intermediate circuit wouldalso be the same. In this case the relay '22C would be in normalposition and the C block would be isolated from block B by the openpoint in the right-hand winding of the transformer ATB as before. Withthe train either block alone as above, the blocks C and D are stillinductively connected with a transposition which neutralizes theinductive disturbance picked up by the intermediate circuit.

It is obvious from the drawings that alternate sections of theintermediate circuit or individual block circuits correspond, that is,section A, B, and E are similar in every respect and sections C, D, andF are similar. The circuits for adjacent blocks in dissimilar sections,such as C and D are in permanent transposed inductive relationship, asdescribed. Assuming now that the train is moving from block C into blockB, relay MB will be short-circuited by the trucks of the locomotive orthe rst car of the train, as the block is entered, and that relay willbecome deenergized. Relay 46B at its upper-back contacts will open apoint in the previously described intermediate circuit of block C, andwill include the right-hand winding of the transformer 4TB in thiscircuit. The short-circuit will be removed from the left-hand winding ofthe transformer 4TB at the lower-back contactsof the relay, and theshort-circuit will be removed from the righthand winding of thetransformer 4TL by the middle-back contacts. The intermediate circuit ofthe block B Will then be exactly the same as that previously describedfor block D and the circuit of the block A will be the same as that ofthe block C as described for the train in block D alone. It, therefore,follows that the intermediate circuits of these four blocks A to D,inclusive, are now inductively connected by the transformers GTA, ATB,and ATC. The windings of the transformer ATC are connected in reversedirections to the adjacent block circuits, as are those of transformersdTA and 4TB. Two additional transpositions are, therefore, inserted inthe circuit which extends over four blocks. Conversation may be heldbetween the front and rear of the train as in the previous instance, orthe dispatcher may call by operating the selector S', as in the previousinstance. Similar conditions will prevail with the train in block B forexample and another train in block C or D. As the rear end of the trainleaves block vC and enters into block B, the circuit of block C revertsto its normal condition, which is the same as that shown for theintermediate circuit of block E. The relay 42C will be deenergized andwill short-circuit the left-hand winding of the transformer 4'IB, at thesame time removing the short-circuit from the right-hand winding of thetransformer 4TL. The inductive connection between the intermediatecircuits B and C will, therefore, be disabled and the talking circuitwill include only the circuits of the blocksA and B, respectively. Thedispatcher will connect to this circuit by operating the selector S toconnect up the left-hand Winding of the transformer 4TL. Thus regardlessof the length of the train or the direction in which it is moving, aneven number of transposed sections will always comprise the intermediatecircuit, Which being thus balanced will effectively neutralize anyinductive disturbance which may be picked up either by the intermediateconductor carried on the pole line, or by the rails.

Referring now to Fig. 6 it will be seen that the signal relay apparatusshown here is identical with that shown in Fig. 4, above described. Arelay such as the relay 63B is bridged across the rails of each blocktogether with a source of current or battery. Alternate blocks such as Cand E are provided with a relay such as 64C in series with the bridgedbattery. These relays have the same function of connecting up theadjacent intermediate circuits as the corresponding relays of the systemdisclosed in Fig. 4. In addition the railroad has been shown equippedfor automatic train control by the intermittent contact method. Thiscontrol apparatus is similar to that shown in the Bulletin No. 5 of theAmerican Railway Association above referred to. The roadside equipmentconsists essentially of a ramp to which bridged across the connection tothe car trucks and the shoe by means of the key 6K. An impedance 6P isinserted in the automatic control circuit to prevent false operationfrom the alternating signalling current. The wayside equipment ismodified by connecting a relay GID in series with a condenser across thetrack rails and the ramp. A impedance 6P! is also connected in the relaycircuit of this apparatus to prevent false operation from thealternating signalling current. on operating a selector, such as S or Sof Fig. 4, connected up the speaking transformer 4TL or 4TL to thedispatchers line. In the present case the selectors S and S are arrangedto complete a circuit for a connecting relay which performs the functionof connecting the intermediate circuit to the dispatchers line. Thisconnecting relay is also operable under control of the relay BIB or GIDwhich is adapted to be operated by the generator connected to theautomatic train control apparatus. The purpose of this arrangement is tomake it possible for the trainmen to call the -dispatcher in certainblocks. That is, it is unnecessary for the trainmen to wait for thedispatcher to complete a connectionwhen such is desired.

Adjacent intermediate circuits are connected in pairs through areversing transformer, as described under Fig. 4, and additional pairsare connected or disconnected as the train moves It will be recalledthat the dispatcher through the various blocks, exactly the same aspreviously described. To initiate a call from the train to thedispatchers office the trainman will actuate key 6K as the train entersthe block D. Current will flow from the output side of the generatorthrough the shoe SH and the ramp RA engaged by the shoe, through therelay SID and its associated condenser, through the track rails andwheel and axle of the car truck, to the key 6K and back to thegenerator. As previously inferred, this alternating current will notaifect the automatic train control apparatus, but will operate the relaySID. Further the entry of the train into the block D will cause thedeenergization of the relay 63D in the usual way, which relay willfunction to connect up the adjacent block circuits and at the same timewill prepare a locking circuit for the relay SRD. Relay li lD onoperating will close an energizing circuit for relay 62D, and that relaywill operate and lock by way of its upper-front contacts and thelowerback contacts to the relay 63D. Relay 62D at its middle-frontcontacts will connect the left-hand winding of the transformer BTL!across the conductors of the dispatchers line and at its lowerbackcontacts will remove the short-circuit from the right-hand winding ofthat transformer. By operating the talking key of the telephone set thetrainmen can now call over the intermediate cir-- cuit and thedispatchers line. The operating circuit of relay 62D may also becompleted by the dispatcher on operating the selector Si. A talkingcircuit, of course, is completed only at times when there is a train inthe block and the relay 63D is deenergized. 'Ihis is of no consequencesince there is no occasion for a talking circuit unless there is a trainin the block.

Talking connections between the head and rear end of the train, orbetween separate trains in `adjacent sections, Will be completed exactlyas described for Fig. 4. In this case no signalling current will beapplied to the relay 6 l D, and consequently the connecting relay 62Dwill not be operated. It may be noted. that under these conditions theright-hand winding of the transformer BTL! is short-circuited. Thisarrangement improves transmission by removing an unnecessary impedancefrom the talking circuit. The various block circuits are connected intransposed pairs and paired circuits are likewise connected intransposed relationship when required.

In Fig. 7 is shown a stretch of track divided into blocks A to F,inclusive, each block being provided with two normally energized bridgedrelays for signalling purposes. 'Ihese relays will become deenergized asthe train passes through a block and complete circuits for talkingpurposes. Assume that the train is in block C, as illustrated and relays'HC and 12C are deenergized. When the telephone set of the train,corresponding to the set shown in Fig. 5, is connected in talkingrelation and current is impressed on the inductor iI, correspondingcurrent is induced in an intermediate circuit, which may be traced fromthe lower rail 2 of block C, through the condenser at the right end ofthe rail, through the upperback contacts of relay HC and upper-frontcontacts of relay 12D, through the upper winding of transformer TRLZ,thence through conductor 'i3 which is carried on the ties parallel tothe rails and located adjacent to the upper rail 2', thence through theupper-back contacts of relay 12C and upper-front contacts of relay TIB,through the condenser, to the left-hand end of the rail 2. With thetrain completely in this block a talking circuit exists between thefront end and the rear end of the train over this inductive intermediatecircuit. The dispatcher may also complete a talking connection with thetrain in this block by operating the selector S2 which connects` up thelower Winding of the transformer TRLZ with the dispatchers line. As thetrain moves into block D, there will be a period when both blocks areoccupied, and relays 'HD and '12D in addition to relays 'HC and 12C'will be deenergized. The previously traced intermediate circuit insteadof extending through the upper-make contacts of relay 12D will beextended through the upperback contacts by way of conductor M whichcorresponds to conductor 13 of block C, thence through the upper windingof transformer TRL3, upper-front contacts of relay 12E, upper-backcontacts of relay HD, through the condenser to the right-hand end of therail 2 of block D, thence through the condenser at the left-hand end ofthis rail and the lower-back contacts of relays 'HC and 12D to conductor13. It will be seen that a transposition exists between these twocircuits, that is, current flowing through conductor 13, block C, willflow through the rail of block D and then through the conductor 'I4 ofthe block D and back to the rail of block C. Talking circuits betweenthe front and rear of the train or between separate trains of these twoblocks may be completed in the usual way. The dispatchers may alsoconnect to this circuit by operating selector S3 which bridges the lowerwinding of the transformer TRL3 vacross the dispatchers line. As the endof the train leaves block C, relays HC and 12C will again becomeenergized and disconnect the intermediate circuit of the block from thatof block D which will now correspond to the circuit rst described forblock C. Thus as the train moves along the intermediate circuit will beprepared andwhen necessary will be connected only in the blocks occupiedby the train.

The above described arrangement is particularly adapted for use insystems using long block sections in which the inductive interference isrelatively small. The use of the conductor between the rails is similarto that of a conductor on a pole line, although it is obviously lessexpensive to use the conductor as shown. In the modiiication shown inFig. '7 the train inductor instead of being mounted vertically, as shownin Fig. 1 will be mounted horizontally so that opposite sides willaifect the two sides of the circuit comprising the conductor 13 and therail 2. Alternatively the inductor may be mounted vertically directlyover the rail or over the conductor, so that the influence will beconfined to one side of the circuit. It is obvious that two rails inparallel may be used in this type of connection, in which case theconductor will be carried down the center of the track and the inductorwill be carried vertically over this conductor.

The system disclosed in Fig. 8 is in general similar to that of Fig. 4of which it is a modification. The signal relay apparatus shown issimilar to that of Fig. 7. In this case, however, each block circuit isnormally isolated from adjacent circuits, but in the case of a blockbeing occupied by a train, two circuits are inductively connected with atransposition. This arrangement may be used to advantage when theinductive disturbances picked up by the intermediate circuit arerelatively uniform throughout its length. In addition, connection withthe dispatchers line is made by means of a third winding on the blockconnecting transformers by the presence of a train in the associatedblock. In other words, the train and the dispatcher are telephonicallyconnected at all times.

By way of example, a train is assumed to be occupying block C. The frontcar or locomotive of the train is provided with a telephone set as Fig.and an inductor such as shown in Fig. 1. When the talking key K of thetelephone set is operated and the transmitter spoken into, thetransmitting amplier impresses current on the inductor I in the usualway and this current in turn is induced in the two track rails of theblock C in parallel. A closed loop circuit may be traced from theright-hand ends of the rails of this block, through the parallelcondensers connected thereto, through the left-hand winding oftransformer ST3, conductor 83, right-hand winding of transformer ST2,lower-back contacts of relay 82C, through the two condensers to theleft-hand end of the rails of block C. A similar circuit for block B isinductively connected to the above circuit in transposed relationship,this circuit extending from the left-hand winding of transformer ST2,conductor 84, lower front contact of relay 82B, through the twocondensers to the left-hand end of the rails of block B, through theserails in parallel and the two condensers connected to the right endthereof, to the left-hand winding of the transformer. Since relay 8| isdeenergized and relay 82D is energized, the middle winding oftransformer ST3 will be bridged across the dispatchers line. Thisarrangement provides a continuous talking connection between the trainand the dispatchers oflice. SinceA trains in other blocks are similarlyconnected to the dispatchers line, messages may be transmitted betweentrains by way of the dispatchers line when the trains occupynon-adjacent blocks.

Having described the invention, what is considered new and is desired tohave protected by Letters Patent is set forth in the following claims:

What is claimed is:

1. In a telephone system for communicating between a moving train and awayside point, the combination with a transmitting and receiving set onthe train, of a transmitting and receiving set at the wayside point, aline for said second set, a plurality of intermediate circuits forindividually inductively connecting the two Sets via said line, andmeans for inductively connecting two of said intermediate circuits overa path independentY of said line. y

2. In a telephone system for communicating between a moving train andawayside point, the combination with a transmitting and receiving set onthe train, of a transmitting and receiving set at the wayside point, aline for said second set, a plurality of intermediate circuitseachassociated with a particular sectionof track, said circuits beingindividually adapted to connect with said line for inductivelyconnecting said two sets when the train occupies the associated tracksection, and means for inductively connecting adjacent circuitsindependent of said line when a train occupies the adjacent tracksections associated with said circuits.

3. In a telephone system for communicating between a moving train and awayside point, a

transmitting and receiving set on the train, a

transmitting and receiving set at the waysidepoint, a plurality ofintermediate circuits each associated with a particular section of trackand adapted to be inductively connected to said first set when the trainoccupies the section, means aie-ice for inductively connecting theintermediate cir-4 cuit of the occupied section with said second set,and means controlled by the train for inductively connecting adjacentcircuits when the train moves into the adjacent section andsimultaneously occupies both sections and for disabling thelastmentioned means of one of the circuits.

4. In a telephone system for communicating between a moving train and awayside point, a telephone set on the train, a telephone set at thewayside point, a plurality of intermediate circuits each associated witha particular section of track and inductively connected with said firstset when a train occupies the section, means for inductively connectingthe circuit associated with the occupied section with said second set,means controlled by the train for inductively connecting the circuitsassociated with adjacent sections occupied by the train, and means fordisabling said connection with the second set responsive to theconnection of said adjacent sections.

5. In a telephone system for communicating between a train and a waysidepoint, a telephone set on the train, a telephone set at the waysidepoint, a plurality of intermediate circuits each associated with aparticular section of track and adapted ,to inductively connect said twotelephone sets when the train moves through the associated section, andmeans for inductively connecting adjacent circuits in transposedrelationship when a train moves from one section to another andsimultaneously occupies two sections.

6. The combination with a railroad track divided into a plurality ofelectrically insulated sections, of a separate closed electrical circuitincluding the track rails for each section, said circuits being adaptedfor inductively connecting with a telephone set carried by a trainoccupying the associated section, and means for inductively connectingadjacent circuits when adjacent sections are simultaneously occupied bya train or trains.

7. The combination with a railroad track divided into a plurality ofelectrically insulated sections, of a plurality of closed electricalcircuits including the track rails of the respective sections, sai-dcircuits being adapted for inductively connecting with a telephone setcarried by a train occupying the associated section, and traincontrolled means for inductively connecting adjacent sections intransposed relationship.

8. The combination of a railroad track divided into a plurality ofelectrically insulated sections, of a train moving along said track, atelephone set on said train, a separate closed circuit including trackrails for each section inductively connected with said telephone set,and train controlled means for inductively connecting adjacent circuitsresponsive to the train moving from one section to another andsimultaneously occupying both sections and for disconnecting the lastcircuit when the associated section is vacated.

9. In an inductive telephone system for communicating between differentpoints on a moving train, an intermediate circuit including track railsfor inductively connecting the telephones at said different points, andmeans for automatically inserting transpositions in said circuit as thetrain moves along the track.

10. In an inductive telephone system for communicating between a movingtrain and a wayside point, an intermediate circuit including track railsinductively connecting the telephone set on the train with the telephoneset at the Wayamarcol side point, and means for automatically insertingtranspositions in said circuit as the train moves along the track.

11. The combination with a railroad track divided into a plurality ofelectrically insulated sections, of a separate closed electrical circuitfor each section including the track rails of the section, anintermediate circuit normally comprising a pair of adjacent sectionalcircuits inductively connected in transposed relationship, and automaticmeans for inductively connecting a plurality of said intermediatecircuits.

l2. The combination with a railroad track divided into a plurality ofelectrically insulated sections, of a separate closed electrical circuitfor each section including the track rails of the section, said circuitsbeing normally connected in pairs with a transposition between thecircuits, and automatic means for connecting adjacent paired circuits intransposed relationship.

13. 'I'he combination with a track comprising a plurality ofelectrically insulated' rail sections, a closed electrical circuit foreach section including the rails of the section, said sections being oftwo different types arranged in alternate positions, an intermediatecircuit normally comprising one circuit of each type inductivelyconnected with a transposition, and automatic means for expanding saidintermediate circuit to include a plurality of circuits of each typeinductively connected with transpositions between circuits.

14. In a railroad telephone system, a track comprising a plurality ofelectrically insulated rail sections, a closed electrical circuit foreach section including the track rails of the section, and a travelingintermediate circuit adapted to inductively connect with a telephone setcarried by a train, said intermediate circuit comprising an even numberof transposedly connected sectional circuits.

15. In a telephone system for communicating between a moving train and awayside point, a telephone set on the train, a telephone set at thewayside point, an intermediate circuit including track rails,inductively connected with said rst set, train controlled means forinserting transpositions in said circuit, and means controlled from thetrain for inductively connecting said circuit with said second set.

16. In a telephone system for communicating between a moving. train anda wayside point, a telephone set on the train, a telephone set at thewayside point, an intermediate circuit including track rails inductivelyconnected with said first set, means controlled by the train forinserting transpositions in said circuit, and means controlledseparately from either the train or the wayside point for inductivelyconnecting said circuit with said second set.

17. In a telephone system for communicating between moving trains andbetween such trains and a wayside point, telephone sets on the trains, atelephone set at the wayside point, a traveling intermediate circuitincluding track rails inductively connecting said first sets, saidcircuit comprising an even number of transposed sections, and traincontrolled means for increasing or decreasing the number of sections insaid circuit.

18. In a telephone system for communicating between the head and rearends of a train or between either end of the train and a waysidestation, telephone sets at each end of the train and at the station, awayside telephone line connected with said station set, intermediatecircuits each associated with a particular section of a track, means forinductively connecting the train sets with the intermediate circuitassociated with the particular section of the track occupied by therespective ends of the train, vmeans effective when the. train occupiesa plurality of sections of track for inductively connecting theassociated circuits to complete a talking connection between the headand rear ends of the train, and means effective when the train occupiesa plurality of sections of track for connecting only one of theassociated circuits to' said line to complete a talking connectionbetween either en'd of the train and said wayside; station.

19. In a telephone system for communicating between a moving train and awayside station, a temporary connection between a transmitting and areceiving set on the train and a transmitting and receiving set at thewayside station comprising a plurality of closed loop circuitsinductively c'onnected together in series relationship, and a telephoneline inductively connected with one, of said circuits'. l

20'. In a telephone system for communicating between a moving train anda wayside station, a temporary circuit connecting the train and waysidestation comprising a plurality of closed loop circuits associated with aparticular section of track, said circuits being inductively connectedin series relationship, a telephone line inductively connected with oneof said circuits, transmitting and receiving sets on the train and atthe wayside station adapted to be inductively connected to one of saidcircuits and to said line respectively, and means associated with eachset for determining whether the connection shall be for transmitting orfor receiving purposes.

21. In anl inductive telephone system for communicating between twopoints on a moving train, an intermediate circuit inductively connectingtelephone sets at said points, and m'eans for automatically insertingtranspositions in said circuit as the train moves along the track.

22. In an inductive telephone system for communicating between twopoints on a moving train, a plurality of stationary section circuits,and means for progressively connecting adjacent section circuits intransposed relationship as the train moves along the track to constitutea traveling intermediate circuit for inductively connecting telephonesets at said two points.

23. The combination with a railroad track divided into a plurality ofsections, a separate closed electrical circuit for each section adaptedto inductively connect with a telephone carried by a train occupying theassociated track section, and means for connecting adjacent circuits intransposed relationship when adjacent sections are occupied by a trainor trains.

24. In an inductive telephone system for communicating between twopoints on a moving train and between either or both of said points and awayside station, telephone sets at said two points and at said waysidestation, a line for said station telephone, an intermediate circuitinductively connected with said rst two telephones and With said line,and train controlled means for inserting transpositions in said circuitas the train moves along the track.

25. The combination with a railroad track divided into sections, of aseparate communicating circuit for each section including the trackrails of the section, a normally energized relay bridged across thetrack rails of one section adapted to be deenergized responsive to theoccupation of the section by a train, a normally deenergized relaybridged across the track rails of an adjacent section adapted to beenergized responsive to the occupation of the section by a train,circuit connections normally effective to isolate said communicatingcircuits, and contacts controlled by said relays for opening saidcircuit connections.

26. In combination, two adjacent sections of railroad track, a source ofcurrent connected across the rails at one end of one section, a relayconnected across the rails at the other end of sai-d one section, arelay and a source of current connected in series across the rails atone end of the other section, a telephone circuit for each sectionincluding the track rails of the section, means for preventing currentow from one telephone circuit to the other, and means controlled by saidrelays jointly for disabling said preventing means.

27. In a train telephone system, a track comprising a plurality ofsections, a circuit for each section including the track rails of thesection, means on a train for inducing voice currents in the circuit ofa section occupied by the train,

means for conning said current to the occupied section, relays foradjacent track sections controlled by the occupancy of their respectivesections, and means controlled by said relays jointly for permitting thecurrents induced in the circuit of one section to oW in the circuit cithe adjacent section When both sections are occupied simultaneously by atrain.

28. The combination, in a railway signal system, comprising a pluralityof blocks, of a loop circuit in each block, means for supplyingoscillations from a vehicle in any block to the loop circuit of therespective block, means for relaying oscillations from each loop circuitto the loop circuit of an adjacent block, means on each Vehicleresponsive to oscillations received from another Vehicle through saidloop circuits, and means responsive to the presence of a vehicle in anyblock to prevent oscillations transmitted by a vehicle in another blockfrom being transmitted past the block which is occupied by said iirstmentioned vehicle.

WILLIAM C. PHEBUS.

